The present invention relates to an electronic musical instrument having a circuit for obtaining a musical-scale clock frequency.
In an electronic musical instrument, in general, an analogue waveform is discretely divided into a number of steps with respect to time. Magnitudes of the steps are converted into corresponding digital values. The digital values converted are stored in a tone waveform signal memory at the addresses corresponding to the steps. For reproduction of the original analogue wave form, the digital values stored in the memory are read out through a successive address shift. Then, the read-out digital values are subjected to digital to analogue conversion. In this case, the cycle of the analogue waveform reproduced depends on the address shift speed. Accordingly, the cycle of the analogue wave form reproduced may be freely controlled by changing the frequency of the clock signal used for address shift.
It is assumed now that the waveform stored in the memory is a musical sound waveform and the reading operation of the memory is performed through repetitive address shifting by a clock signal. In this case, the frequency of the reproduced musical sound wave form is determined by the clock frequency, i.e. the number of clock signals per unit time. Accordingly, if the reproduced sound waveform is converted into sound by a speaker, the pitch of the reproduced musical sound is variable by changing the number of clocks per unit time.